FIG. 1 of DE 196 29 203 A1 discloses a rocker arm comprising a lash adjusting element in a bore on its underside, which lash adjusting element can be supplied through a longitudinally extending primary passage with hydraulic medium from the transverse bore of the rocker arm. Air accumulated in an undesired manner in the lash adjusting element or its surroundings can be led to the outside through a venting passage. In the course of this, a slight quantity of hydraulic medium also escapes through the venting passage to the upper side of the rocker arm and spreads over this finally in an uncontrolled manner.
A lubrication of a contact surface of the rocker arm on the other end, not disclosed on the right in the drawing, on the underside is effected only through an oil mist or through a separate injection bore which starts from the transverse bore. A supply of lubricant to the injection bore is affected at the same time as the supply to the primary passage from the rocker arm axle. In this case, the latter cannot comprise a circumferential groove for taking off the hydraulic medium because only a spot injection for avoiding loss of hydraulic medium is desired. Therefore, as a rule, this axle comprises only a segmental groove and thus has to be installed in a correct orientation which leads to an increase of the total costs of the valve train.
Reference is further made to DE 197 18 794 A1, DE 1 301 823 and DE 1 751 416.